Japanese sword question

[sakimori]

Hola,Kubur,
After putting the words(盛常) on YahooJapan and searched it,I believe it is the name of the bladesmith,since that indeed is a common(?)name of Japaneses.
I am affraid of that is all information I have though.Have very little interest into Japanese weapons and not able to read Japanese.
Wish your friend get better help&information.